Reversible circulation internal fan kiln



June 9, 1925. 1,541,443

R.THELEN REVERSIBLE CIRCULATION INTERNAL FAN 'KILN Original Filed April 19, 1924 3 Sheets-Sheet 1 A I [A Fig-l INVENTOR.

OLF WELEN mix 2L BY R A TTORNEYS.

June 9, 1925. 1,541,443

' R. THELEN REVERSIBLE CIRCULATION INTERNAL FAN KILN ori inal Filed April 19, 1924 3 Sheets-Sheet 2 QED INVENTOR. fl 110w l HELEN A TTORNEYS.

June 9, 1925.

R. THELEN REVERSIBLE CIRCULATION INTERNAL FAN KILN 3 Sheets-Sheet 3 Original Filed April 19, 1924 mmvron.

o F HELEN Mg, a BY flm wajm ATTORNEYS.

Patented June 9, 1925.

ROLF THELEN, 0E MADISON, WISCONSIN;

DEDICATED, BY MESNE ASSIGNMENTS, TO

THE PEOPLE OF THE UNITED STATES.

REVERSIBLE CIRCULATION INTERNAL FAN KILN.

Original application filed April 19, 1:924,'Seria1 No. 708,323. Divided and this application filed March Serial No. 14,423.

(GRANTED UNDER THE ACT OF MARCH 3, 1883; 22 STAT. L. 625.)

To all whom it may concern:

Be it known that I, ROLF THELEN, a citi zen of the United States of America, and an employee of the Department of Agriculture, residing in Madison, Wisconsin (whose postoifice address is Forest Products Laboratory, Madison, Wisconsin), have invented a new and Improved Reversible Circulation Internal Fan Kiln.

This application is a division of an application filed April 19, 1924, which bears Serial Number 7 08,323.

This application is made under the act of March 3, 1883, Chapter 143 (22 Stat. 625), and the invention herein described and claimed may be used by the Government of the United States, its officers and employees, and by any person in the United States without the payment to me of any royalty thereon. I hereby dedicate the same to the free use of the Government and the people of the United States. Y

My' invention consists in an improvement in the design of forced circulation kilns or chambers for drying and conditioning lumber or similar material. However, its use is not limited to wood or wood products. It consists in the adaptation of fans of the disk type, or similar types, to the production of a unique internal circulation of air and the vapor in the kiln combined with the production and regulation of the heat and the humidity within the kiln.

This invention is illustrated in Figures 1 to 3. Figure 1 represents a cross-sectional elevation. Figure 2 represents a horizontal section partly above and partly below the rails. Figure 3 represents a longitudinal sectional elevation taken approximately through the center of the kiln.

The principal feature which I claim as novel and an improvement over existing kilns is the use and arrangement .of the fans and the air distributing system. 'This arrangement is-such that a very fast and uniform circulation of air and vapor through the piles of lumber may be secured and it permits the periodic reversal of the direction of the air movement by simply reversing the direction of rotation of the fans. The air distributing system provides a very, uniform flow of air throughout the length and breadth of the kiln and eliminates the kilns employing centrifugal blowers, and

the disk fans operate very efficiently at these low pressures. Measurements recently made indicate that the static pressures necessary for the successful operation of this system are materially less than one-eighth of an inch of water pressure. It is possible, therefore, by the use of this invention to produce a very great and uniform circulation of air and vapor within the kiln with a very small expenditure of power.

While it is obvious that there are many possible ways in which the use of internal fans can be adapted to dry kilns of different types, this invention is limited to double track kilns in which the lumber is edge stacked. Inv edge stacked lumber the width of each board is in a vertical direction, the thickness and length being in horizontal directions.

Any well-known means of heating the air and the vapor inthe kiln may be used in conjunction with this invention. When steam pipes are used they may be arranged beneath the lumber piles at the sides of the kiln or in any other convenient manner.

Any. convenient form and arrangement of make use of any other well-known and suitserve to prevent the circulation from bylongitudinal motion.

passing the fans. BB arethe fans producing the circulation. Straight-bladed disk fans are preferable. Any type of fan, however, in which the reversal of the direction of rotation of the fan produces a reversal in the direction of the flow of the air current passing through the fan can be used. The two fans on each shaft are of opposite pitch so that when the shaft is rotated the two fans blow either towards each other or away from each other. CC are the shafts upon which the fans are mounted. Provision is made to take care of the expansion and contraction of these shafts with changes in the temperature in the kiln and to take care of the thrust of the fans. This provision consists in equipping one of the bearings II with suitable thrust rings or collars and equipping all of the other bearin II on each shaft with any well-known means for Plain bearings and roller bearings require no special provision of this kind. Certain types of ball bearings require housings which permit the entire hearings to slide longitudinally within them. DD are the air inlet dampers used to re 11- late and control the amount of air entering the kiln from the outside. EE are the heating coils. These may be of the return bend type or other convenient type. FF are the steam jet pipes used to increase the humidity of the air in the kiln. Suitable o enings are provided to permit the'escape of the steam throughout the length of the kiln. Various other common and well-known arrangements may be used. GG are the lumber-supporting trucks. HH are the shaft hangers. II are bearings for the shafts CC. JJ are the tracks upon which the lumber-supporting trucks run. KK are the side walls of the kiln. LL is the lumber to be driedQ M are the track supports. 00 are air outlet dampers for controlling the-amount of air being exhausted from the kiln. RR are the motors which furnish the power to drive the fans. SS are switches for controlling the speed and rotation of the motor armature. The motors RR are direct-connected to their respective shafts. While the drawings show and the specification describes electric motors, any other suitable driving means may be used. TT are air inlet fiues in which the dampers DD are fitted. UU are the air outlet flues in which the dampers 00 are fitted. lVVV are the side air passages between the pilles of lumber and the side walls of the 1 n. YY are the second diffusers. .Z is the first diffuser. The plenum chamber between the second diffusers and the first diffuser is the secondary plenum chamber. lVhile the drawings show and the specification describes certain specific arrangement of the fans and shafts, this invention is not limited to this particular arrangement, since it is obvious that its functions can be performed in an equivalent manner with ments of the fans.

The operation of the kiln is briefly as follows: The lumber is placed in the kiln, the doors and all of the dampersare closed, and

the kiln is started. Steam is turned into the coils and the steam jets are turned on. Suitable regulatlng devices are provided to control and regulate the supply of steam to the heating coils and the supply of the steam to the steam jets. If it is'found impossible to reduce the humidity to the desired point with the steam 'ets all turned off, the dampers- DD and O are opened to allow fresh air. to enter and moist air to escape. These dampers should be adjusted so that a humid- XX are the main air distributors.

other arrangeity below that desired will be secured. The

steam jets may then supply a suflicient amount of steam to bring the humidity up to the desired point. Assuming that the direction of rotation of the fans is such that the air and vapor move upward through the lumber piles LL they will pass downward through the side air passages WW, throu rh the fans BB, overrthe heating coils E through the first diffuser Z, through the second diffusers YY, and then upward through the lumber again. When the direction of rotation of they fans is reversed the direction of the circulation of air and vapor is likewise reversed. When the direction of the air circulation is upward through the lumber piles LL the plenum chamber in which the heating coils EE are located and the secondary plenum chamber between the diffusers YY and Z will be under slight pressure. (hen the circulation is reversed they will be under. a slight vacuum. F urthermore, theside passages'W'W will be unthe plenum chambers is so small that the I velocity head can not be measured with manometers and similar instruments usually used for the purpose.

, It is well understood that when the circulation of the air. and the vapor in the kiln is continuously in one direction, that portion of the pile at which the air enters will dry more rapidly than the opposite side since the air in its passage through the lumber picks up moisture and thus reduces its drying capacity. The reversal of the direction 'of the air circulation overcomes this defect since that edge of each lumber pile which was the entering air edge before reversal becomes the leaving air edge after reversal. Those portions of the piles which dried fastest before reversal dry most slowly after reversal. The reversal of the circulation will in practice be done periodically every two or three days or oftener, the exact period being determined by the condition of the lumber in the kiln;

Several arrangements of the plenum chambers are possible and practicable. The principal'object of the plenum chambers and diffusers is to produce a uniform flow of air and vapor through thelumber to be dried, and any detailed arrangement which will accomplish this result will be satisfactory if at the same time it does not consume an excessive amount of power. 1

Having fully described the principles of vapor through the fans themselves 1. Ina doubletrack dry kiln arranged for edge stacking: a series of cross shafts; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; two. fans of opposite pitch mounted for rotation on each shaft; and an air distributing system'comprising a main air distributor and two sets of diffusers.

2. In a double track dry kiln arranged for edge stacking: a series of cross shafts; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet flues and dampered air outlet flues; two fans of opposite pitch mounted for rotation on each shaft; and an air distributing system comprising a main air distributor and two sets of diffusers. 3. In a double track dry kiln arranged for edge stacking: a series of cross shafts; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet flues and dampered air outlet flues; means for heating the kiln and its contents; two fans of opposite pitch mounted for rotation on each shaft; and an air distributing system' comprising a main air distributor and two sets of diffusers.

4. In a double track drykiln arran ed' for edge stacking: a series of cross sha ts; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet flues and dampered air outlet flues; means for heating the kiln and its contents; means for humidifying the atmosphere in the kiln; two fans of opposite pitch mounted for rotation on each shaft; and an airidistributing system comprising a main air distributor and two sets of diffusers.

February 18, 1925.

ROLF THELEN. 

